Hollow drug-filled stent and method of forming hollow drug-filled stent

ABSTRACT

A stent is formed from a wire that in cross-section includes an outer member having a lumen and a radiopaque core member partially filling the lumen. A substance for elution through openings formed through the outer member fills the portion of the lumen not filled by the radiopaque core member. In a method of forming the stent, a composite wire including an outer member and a dual core member is shaped into a stent pattern. The dual core member includes a first core member and a second, radiopaque core member. The shaped composite wire is processed to remove the first core member from the outer member without adversely affecting the outer member and the second core member. The portion of the lumen that was occupied by the first core member may be filled with a substance for elution through openings from through the outer member to the lumen.

FIELD OF THE INVENTION

The present invention relates hollow drug-filled stents and methods offorming hollow-drug-filled stents, and in particular, hollow-drug filledstents with improved radiopacity.

BACKGROUND OF THE INVENTION

Drug-eluting implantable medical devices such as stents have becomepopular in recent times for their ability to perform their primaryfunction (such as structural support) and their ability to medicallytreat the area in which they are implanted.

For example, drug-eluting stents have been used to prevent restenosis incoronary arteries. Drug-eluting stents may administer biologically orpharmacologically active substances such as anti-inflammatory compoundsthat block local invasion/activation of monocytes, thus preventing thesecretion of growth factors that may trigger VSMC proliferation andmigration. Other potentially anti-restenotic compounds includeanti-proliferative agents, such as chemotherapeutics, which includerapamycin and paclitaxel. Other classes of drugs such asanti-thrombotics, anti-oxidants, platelet aggregation inhibitors andcytostatic agents have also been suggested for anti-restenotic use.

Drug-eluting medical devices may be coated with a polymeric materialwhich, in turn, is impregnated with a biologically or pharmacologicallyactive substance or a combination of biologically or pharmacologicallyactive substances. Once the medical device is implanted at a targetlocation, the biologically or pharmacologically active substance isreleased from the polymer for treatment of the local tissues. Thebiologically or pharmacologically active substance is released by aprocess of diffusion through the polymer layer for biostable polymers,and/or as the polymer material degrades for biodegradable polymers.

Controlling the rate of elution of a biologically or pharmacologicallyactive substance from the impregnated polymeric material is generallybased on the properties of the polymer material. However, at theconclusion of the elution process, the remaining polymer material insome instances has been linked to an adverse reaction with the vessel,possibly causing a small but dangerous clot to form. Further, drugimpregnated polymer coatings on exposed surfaces of medical devices mayflake off or otherwise be damaged during delivery, thereby preventingthe biologically or pharmacologically active substance from reaching thetarget site. Still further, drug impregnated polymer coatings arelimited in the quantity of the biologically or pharmacologically activesubstance to be delivered by the amount of a drug that the polymercoating can carry and the size of the medical devices. Controlling therate of elution using polymer coatings is also difficult.

Accordingly, stents with hollow, drug-filled structural members havealso been contemplated. For example, U.S. Pat. No. 6,071,305 to Brown etal. generally discloses a stent formed of an elongated member in aspiral tube configuration. The elongated member includes a groove thatcan be filled with an active agent. Further, U.S. ApplicationPublication No. 2011/0008405 to Birdsall et al. and U.S. ApplicationPublication No. 2011/0070358 to Mauch et al., each of which isincorporated by reference herein in its entirety, describe methods offorming stents with hollow-drug-filled structural members from compositewires. However, preferred structural members for stents, such asnickel-titanium alloys (“nitinol”) and alloys of cobalt, nickel,chromium and molybdenum (“MP35N”, “MP20N”) are relatively radiolucent,especially when hollow. Thus, there is a need for a stent withhollow-drug filled structural members with improved radiopacity.

SUMMARY OF INVENTION

Embodiments hereof relate to a stent with hollow, drug filled struts andcrowns. The struts and crowns are formed from a wire. The wire includesan outer member or shell and a lumen. A portion of the lumen is filledwith a radiopaque material continuously along the length of the wire. Inone embodiment, the overall lumen is generally circular and theradiopaque material is generally D-shaped, thereby leaving a generallyD-shaped open lumen that may be filled with a biologically orpharmacologically active agent.

Embodiments hereof also relate to a method of forming a stent. Acomposite wire including an outer member and a dual core member disposedwithin the lumen of the outer member is shaped into a stent pattern. Thedual core member includes a first core member and a second core member.The shaped composite wire is processed such that the first core memberis removed from the lumen of the outer member without adverselyaffecting the outer member and the second core member, such as bychemical etching. Openings may be provided through the outer member tothe lumen of the outer member before or after the processing step. Theportion of the lumen where first core member was removed may be filledwith a biologically or pharmacologically active substance to be elutedthrough the openings provided through the outer member.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of the invention as illustratedin the accompanying drawings. The accompanying drawings, which areincorporated herein and form a part of the specification, further serveto explain the principles of the invention and to enable a personskilled in the pertinent art to make and use the invention. The drawingsare not to scale.

FIG. 1 is a schematic illustration of an exemplary stent in accordancewith an embodiment hereof.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a longitudinal cross-section of an end of the wire of thestent of FIG. 1.

FIG. 4 is a schematic illustration of a composite wire including anouter member, a first core member, and a second core member.

FIG. 5 is flow chart illustrating an embodiment of a method of forming ahollow wire stent including a radiopaque core.

FIGS. 6-9 are cross-sectional views of the composite wire of FIG. 4 atvarious stages of the method of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention are now described withreference to the figures, where like reference numbers indicateidentical or functionally similar elements.

An embodiment of a stent 100 disclosed herein is shown in FIGS. 1-3. Inparticular, stent 100 is formed from a hollow wire 102, wherein a lumen103 of the hollow wire 102 is partially filled with a radiopaque coremember 124. The term “wire” as used herein means an elongated element orfilament or group of elongated elements or filaments and is not limitedto a particular cross-sectional shape or material, unless so specified.In the embodiment shown in FIG. 1, hollow wire 102 is formed into aseries of generally sinusoidal waveforms including generally straightsegments or struts 106 joined by bent segments or crowns 108 and thewaveform is helically wound to form a generally tubular stent 100. Inthe embodiment shown in FIG. 1, selected crowns 108 of longitudinallyadjacent sinusoids may be joined by, for example, fusion points 110. Theinvention hereof is not limited to the pattern shown in FIG. 1. Wire 102of stent 100 can be formed into any pattern suitable for use as a stent.For example, and not by way of limitation, wire 102 of stent 100 can beformed into patterns disclosed in U.S. Pat. No. 4,800,882 to Gianturco,U.S. Pat. No. 4,886,062 to Wiktor, U.S. Pat. No. 5,133,732 to Wiktor,U.S. Pat. No. 5,782,903 to Wiktor, U.S. Pat. No. 6,136,023 to Boyle, andU.S. Pat. No. 5,019,090 to Pinchuk, each of which is incorporated byreference herein in its entirety. Further, instead of a single length ofwire formed into a stent pattern, a plurality of wires may be formedinto a two-dimensional waveform and wrapped into individual cylindricalelements. The cylindrical elements may then be aligned along a commonlongitudinal axis and joined to form the stent.

As shown in FIG. 2, hollow wire 102 of stent 100 includes a radiopaquecore member 124 that occupies a portion of the lumen 103 of hollow wire102. Radiopaque core member 124 allows stent 100 to be visible underX-ray or fluoroscopic imaging equipment when outer member 102, describedbelow, is made of a material that is not sufficiently radiopaque to bevisible under X-ray or fluoroscopic imaging equipment. Thus radiopaquecore member 124 is more radiopaque than outer member 102. The term“radiopaque” refers to the ability of a substance to absorb or attenuateX-rays. Few substances will transmit 100% of X-rays and few substanceswill absorb 100% of X-rays. For the purposes of this disclosure,radiopaque will refer to those substances or materials which are capableof being imaged by an X-ray imaging device such as but not limited to afluoroscope. The remaining portion of lumen 103 allows for abiologically or pharmacologically active substance 112 to be depositedthere within. Although hollow wire 102 is shown as generally having acircular cross-section, hollow wire 102 may be generally elliptical orrectangular in cross-section. Hollow wire 102 further includes cuts oropenings 104 dispersed along its length to provide access to lumen 103to permit biologically or pharmacologically active substance 112 to bereleased from lumen 103. Openings 104 may be disposed only on struts 106of stent 100, only on crowns 108 of stent 100, or both struts 106 andcrowns 108. Openings 104 may be sized and shaped as desired to controlthe elution rate of biologically or pharmacologically active substance112 from stent 100. Larger sized openings 104 generally permit a fasterelution rate and smaller sized openings 104 generally provide a slowerelution rate. Further, the size and/or quantity of openings 104 may bevaried along stent 100 in order to vary the quantity and/or rate ofbiologically or pharmacologically active substance 112 being eluted fromstent 100 at different portions of stent 100. Openings 104 may be, forexample and not by way of limitation, 5-30 μm in diameter. Openings 104are provided to access the portion of lumen 103 with biologically orpharmacologically active substance and may be provided on an outwardlyfacing or abluminal surface 116 of stent 100, as shown in FIG. 2, or onthe inwardly facing or luminal surface 118 of stent 100, or may beprovided anywhere along the circumference of wire 102 provide that theopenings 104 provide access to the portion of lumen 103 withbiologically or pharmacologically active substance 112. Openings 104 mayhave a constant diameter through the depth or have a tapered or conicalshape.

Ends 114 of wire 102 may be closed, as shown in FIG. 3. Ends 114 may beclosed by crimping excess material of wire 102 to close lumen 103.Closing ends 114 prevents biologically or pharmacologically activesubstance 112 from prematurely releasing from ends 114. However, closingends 114 is not required as substance 112 may be dried, provided withina polymer matrix, enclosed within a liner (not shown), or otherwiseprotected from premature release from ends 114. Further, ends 114 may bewelded, crimped or otherwise connected to other portions of wire 102such that the ends 114 are not free ends. Ends 114 may alternatively beprovided as free ends.

FIGS. 4-9 show a method for forming a hollow wire stent in accordancewith an embodiment hereof. As shown in FIG. 5, step 200 is to utilize acomposite wire 170 having an outer member 102 and a dual core member 120disposed within a lumen 103 of outer member 102, as shown schematicallyin FIG. 4. Dual core member 120 is formed from a first core member 122and a second core member 124. Outer member 102 becomes hollow wire 102of stent 100, and thus has been labeled with the same reference number.Second core member 124 is formed from a radiopaque material and becomesradiopaque core member 124 shown in FIGS. 2-3. Composite wire 170 may beformed by any method known in the art, for example and not by way oflimitation, a drawn filled tubing process, extrusion, or any othersuitable method. In one example, first and second core members may 122,124 may each be machined into a D-shaped or semi-circular cross-sectionfrom a respective rod. The flat sides of the D-shaped first and secondcore members may be placed side by side to form a cylindrical rod. Thedual core member 120 may then be encapsulated by outer member 102, suchas by methods of forming composite wires known to those skilled in theart. Examples of composite wires and methods of forming composite wirescan be found in U.S. Pat. No. 5,630,840 to Mayer, U.S. Pat. No.6,248,190 to Stinson, U.S. Pat. No. 6,497,709 to Heath, and U.S. Pat.No. 7,101,392 to Heath, each of which is incorporated by referenceherein in its entirety.

Outer member 102 may be any material that is suitable to be used as astent, provided that it survives the process of removing first coremember 122, as described in more detail below. For example and not byway of limitation, outer member 102 may be a stainless steel, “MP35N,”“MP20N,” nickel titanium alloys such as Nitinol, magnesium, L605, orcombinations thereof. “MP35N” and “MP20N” are trade names for alloys ofcobalt, nickel, chromium and molybdenum available from standard PressSteel Co., Jenkintown, Pa. “MP35N” consists of 35% cobalt, 35% nickel,20% chromium, and 10% molybdenum. “MP20N” consists of 50% cobalt, 20%nickel, 20% chromium, and 10% molybdenum. The requirements for thematerial of outer member 102 are that it be biocompatible, sufficientlyresilient to be used as a stent, and that it survives the process foreliminating first core member 122, as discussed in more detail below.

First core member 122 and second core member 124 may be made ofmaterials that have a similar stiffness, such that their geometries aresimilar after processing to form composite member 170 and to shapecomposite member into a stent form, as described in more detail below.Further, second core member 124 is made of a radiopaque material thatsurvives the process for removing first core member 122. In anon-limiting example, outer member 102 is made of MP35N, first coremember 122 is made of tantalum, and second core member 124 is made of aplatinum-iridium alloy such as Pt10Ir or Pt20Ir. Pt10Ir is aplatinum-iridium alloy containing about 90% platinum by weight and about10% iridium by weight. Similarly, Pt20Ir is a platinum-iridium alloycontaining about 80% platinum by weight and about 20% iridium by weight.Other examples of material combinations of outer member 102, first coremember 122 (sacrificial material), second core member 124 (survivorradiopaque material), and an etchant as described in detail below,include, but are not limited to those listed in the following table:

Second Core Member Outer Member First Core Member (survivor MaterialEtchant (sacrificial material) material) MP35N, L605, Nitinol XeF₂tantalum, tungsten, platinum, molybdenum, platinum- niobium, rhenium,iridium carbon, germanium, alloys silicon MP35N, L605, 316L, highsilver, copper, tantalum, tantalum, tungsten, temperature aluminumtungsten, molybdenum, platinum, molybdenum-rhenium platinum- alloyiridium alloys Stainless Steel nitric acid copper platinum, platinum-iridium alloys

A cross-section of composite wire 170 is shown in FIG. 6. Outer member102 may have an outer diameter D1 in the range of 0.0025 inch to 0.010inch and wall thickness T in the range of 0.0005 inch or larger,depending on the application, for example, in what lumen or organ andfor what purpose the stent is to be utilized. Accordingly, dual coremember 120 may have an outer diameter of 0.0002 inch to 0.0095 inch. Thevalues listed above are merely examples and other diameters andthicknesses may be used depending on, for example, the materials used,the desired stent shape, and the purpose or location of the stent.

Referring back to FIG. 5, step 210 is to shape the composite wire 170into the stent pattern. As discussed above, the stent pattern can be thepattern shown in FIG. 1 or any other suitable pattern formed from awire. Further, although the order of all the steps is not critical, step210 should be done prior to removing first core member 122, as explainedin more detail below. However, the step of shaping the composite member170 into the stent pattern does not have to include shaping compositemember 170 into the final stent pattern. For example, the step 210 ofshaping the composite member 170 into a stent pattern may include onlyforming the struts 106 and crowns 108 in composite wire 170. Shapingcomposite wire 170 into the stent pattern while dual core member 120 isdisposed within outer member 102 helps prevent kinking or otherdeformations from occurring in outer member 102. Shaping the compositewire 170 into the stent pattern shown in FIG. 1 generally includes thesteps of forming composite wire 170 into a two dimensional waveformpattern followed by wrapping the pattern around a mandrel, as known tothose skilled in the art. The end result is a helical stent patternformed onto a mandrel. Selected crowns 108 of the helical pattern maythen be fused together and the stent may be removed from the mandrel.Step 210 of shaping composite wire 170 into the stent pattern can beperformed with techniques known to those skilled in the art. Forexample, and not by way of limitation, forming the composite wire 170into a two dimensional waveform can be achieved using techniquesdescribed in U.S. Application Publication Nos. 2010/0269950 to Hoff etal. and 2011/0070358 to Mauch et al., and co-pending U.S. applicationSer. Nos. 13/191,134 and 13/190,775, filed Jul. 26, 2011, each of whichis incorporated in its entirety by reference herein. Other techniquesknown to those skilled in the art could also be used.

Step 220 shown in FIG. 5 is to provide openings 104 in outer member 102.Openings 104 may be laser cut, drilled, etched, or otherwise provided inouter member 102. Step 220 need not be performed after step 210, norbefore step 230, although it is preferred to be before step 230, asexplained in more detail below. If step 220 is performed after step 210,a cross-section of composite wire 170 will include outer member 102,dual core member 120, and an opening 104, as shown in FIG. 7.

Step 230 is to remove first core member 122 from lumen 103 of outermember 102 without adversely affecting outer member 102 or second coremember 124, such as by chemical etching. Step 230 can be performed byany suitable process for removing first core member 122 while preservingouter member 102 and second core member 124. In particular, exposingcomposite wire 170 to xenon difluoride (XeF₂) gas at low pressure 1-6Tarr and relatively high temperature (approximately 150° C.) causes thexenon difluoride (XeF₂) gas to react with a tantalum (Ta) first coremember 122 to form TaF₅ and Xe gases, which can be exhausted from lumen103. Xenon difluoride (XeF₂) gas reacts similarly with a first coremember 120 made from tungsten, molybdenum, niobium, rhenium, carbon,germanium, and silicon. However, xenon difluoride (XeF₂) gas does notreact with an outer member 102 formed of MP35N or a second core member124 formed of platinum-iridium alloys such as Pt20Ir and Pt10Irdescribed above, or other materials including, but not limited to, thosematerials listed in the table above. Accordingly, after step 230 iscompleted, outer member 102 and second core member 124 remain, and firstcore member 122 has been removed, leaving the cross-sectional structureshown in FIG. 8. As noted above, openings 104 do not need to be formedprior to the step of removing first core member 122 as long as there isa way to expose first core member 122 to the etchant. For example, ends114 of the wire may be open or temporary ports may for formed throughouter member 102 to expose first core member 122 to the etchant.

Although a particular embodiment of an outer member 102 made from MP35N,a first core member 122 made from tantalum, a second core member 124made from a platinum-iridium ahoy, and a xenon difluoride etchant hasbeen described, those skilled in the art would recognize othercombinations of materials and etchants that could be utilized. Forexample, and not by way of limitation, the material and etchant/removalprocess combinations listed in the table above may be used. Thedescription in the table of the etchant as “high temperature” comprisesexposing the composed wire to a temperature high enough to melt thematerial of the first core member 122 but not sufficiently high to meltthe material of the outer member 102 or the second core member 124.Further, other materials and methods for removing core members may used,as described, for example, in U.S. Application Publication no.2011/0008405 to Birdsall et al. and U.S. Application Publication No.2011/0070358 to Mauch et al., each of which is incorporated by referenceherein in its entirety.

After first core member 122 has been removed, biologically orpharmacologically active substance 112 may be injected into lumen 103 ofouter 102, as shown in step 240 of FIG. 5. This produces a hollow wireor outer member 102 with a radiopaque core member 124 partially fillingthe lumen 103 of the outer member 102 and biologically orpharmacologically active substance 112 filling the portion of the lumen103 not occupied by the radiopaque core member, and openings 104 throughwhich biologically or pharmacologically active substance 112 may beeluted, as shown in FIGS. 2 and 9. Filling lumen 103 with a biologicallyor pharmacologically active substance may be accomplished by any meansknown to those skilled in the art. For example, and not by way oflimitation, methods for filling lumens of hollow wires described in U.S.Application Publication No. 201110070357 to Mitchell et al., which isincorporated by reference herein in its entirety; and co-pending U.S.application Ser. Nos. 12/884,362; 12/884,451; 121884,501; 12/884,578;12/884,596 each filed on Sep. 17, 2010, and each of which isincorporated by reference herein in its entirety.

The biologically or pharmacologically active substance 112 may include.,but is not limited to, antineoplastic, antimitotic, antiinflammatory,antiplatelet, anticoagulant, antifibrin, antithrombin,antiproliferative, antibiotic, antioxidant, and antiallergic substancesas well as combinations thereof. Examples of such antineoplastics and/orantimitotics include paclitaxel (e.g., TAXOL® by Bristol-Myers SquibbCo., Stamford, Conn.), docetaxel (e.g., Taxotere® from Aventis S. A.,Frankfurt, Germany), methotrexate, azathioprine, vincristine,vinblastine, fluorouracil, doxorubicin hydrochloride (e.g., Adriamycin®from Pharmacia & Upjohn, Peapack N.J.), and mitomycin (e.g., Mutamycin®from Bristol-Myers Squibb Co., Stamford, Conn.). Examples of suchantiplatelets, anticoagulants, antifibrin, and antithrombins includesodium heparin, low molecular weight heparins, heparinoids, hirudin,argatroban, forskolin, vapiprost, prostacyclin and prostacyclinanalogues, dextran, D-phe-pro-arg-chloromethylketone (syntheticantithrombin), dipyridamole, glycoprotein IIb/IIIa platelet membranereceptor antagonist antibody, recombinant hirudin, and thrombininhibitors such as Angiomax™ (Biogen, Inc., Cambridge, Mass.). Examplesof such cytostatic or antiproliferative agents include ABT-578 (asynthetic analog of rapamycin), rapamycin (sirolimus), zotarolimus,everolimus, angiopeptin, angiotensin converting enzyme inhibitors suchas captopril (e.g., Capoten® and Capozide® from Bristol-Myers SquibbCo., Stamford, Conn.), cilazapril or lisinopril (e.g., Prinivil® andPrinzide® from Merck & Co., Inc., Whitehouse Station, N.J.), calciumchannel blockers (such as nifedipine), colchicine, fibroblast growthfactor (FGF) antagonists, fish oil (omega 3-fatty acid), histamineantagonists, lovastatin (an inhibitor of HMG-CoA reductase, acholesterol lowering drug, brand name Mevacor® from Merck & Co., Inc.,Whitehouse Station, N.J.), monoclonal antibodies (such as those specificfor Platelet-Derived Growth Factor (PDGF) receptors), nitroprusside,phosphodiesterase inhibitors, prostaglandin inhibitors, suramin,serotonin blockers, steroids, thioprotease inhibitors,triazolopyrirnidine (a PDGF antagonist), and nitric oxide. An example ofan antiallergic agent is permirolast potassium. Other biologically orpharmacologically active substances or agents that may be used includenitric oxide, alpha-interferon, genetically engineered epithelial cells,and dexamethasone. In other examples, the biologically orpharmacologically active substance is a radioactive isotope forimplantable device usage in radiotherapeutic procedures. Examples ofradioactive isotopes include, but are not limited to, phosphorus (P³²),palladium (Pd¹⁰³), cesium (Cs¹³¹), Iridium (I¹⁹²) and iodine (I¹²⁵).While the preventative and treatment properties of the foregoingbiologically or pharmacologically active substances are well-known tothose of ordinary skill in the art, the biologically orpharmacologically active substances are provided by way of example andare not meant to be limiting. Other biologically or pharmacologicallyactive substances are equally applicable for use with the disclosedmethods and compositions.

Further, a carrier may be used with the biologically orpharmacologically active substance. Examples of suitable carriersinclude, but are not limited to, ethanol, acetone, tetrahydrofuran,dymethylsulfoxide, a combination thereof, or other suitable carriersknown to those skilled in the art. Still further, a surfactant may beformulated with the biologically or pharmacologically active substanceand the solvent to aid elution of the biologically or pharmacologicallyactive substance.

Stent 100 may be used conventionally in blood vessels of the body tosupport such a vessel after an angioplasty procedure. It is known thatcertain biologically or pharmacologically active substances eluted fromstents may prevent restenosis or other complications associated withangioplasty or stents. Stent 100 may alternatively be used in otherorgans or tissues of the body for delivery of biologically orpharmacologically active substance to treat tumors, inflammation,nervous conditions, or other conditions that would be apparent to thoseskilled in the art.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofillustration and example only, and not limitation. It will be apparentto persons skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention. Thus, the breadth and scope of the present inventionshould not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the appendedclaims and their equivalents. It will also be understood that eachfeature of each embodiment discussed herein, and of each reference citedherein, can be used in combination with the features of any otherembodiment. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the detailed description. All patents andpublications discussed herein are incorporated by reference herein intheir entirety.

What is claimed is:
 1. A stent comprising: a wire formed into stentpattern, wherein a cross-section of the wire includes, an outer memberhaving a lumen, a radiopaque member disposed within and filling a firstportion of the lumen, and a biologically or pharmacologically activesubstance disposed in a second portion of the lumen; and at least oneopening disposed through the outer member through to the second portionof the lumen;
 2. The stent of claim 1, wherein the radiopaque member iscontinuous through the length of the wire.
 3. The stent of claim 1,wherein the outer member is formed from a material selected from thegroup consisting of stainless steel, nickel-titanium alloys, andcobalt-nickel-chromium-molybdenum alloys.
 4. The stent of claim 1,wherein the radiopaque core member is formed from the group consistingof platinum, platinum-iridium alloys, tantalum, and tungsten.
 5. Thestent of claim 1, wherein the radiopaque core member is D-shaped irecross-section and the first portion of the lumen is approximately halfthe size of the lumen.
 6. The stent of claim 1, wherein the biologicallyor pharmacologically active substance is selected from the groupconsisting of antineoplastic, antimitotic, antiinflammatory,antiplatelet, anticoagulant, anti fibrin, antithrombin,antiproliferative, antibiotic, antioxidant, and antiallergic substancesas well as combinations thereof.
 7. A method of forming a stentcomprising the steps of: shaping a composite wire into a stent pattern,wherein the composite wire comprises an outer member and a dual coremember disposed within a lumen of the outer member, wherein the dualcore member comprises a first core member and a second core member;processing the composite wire such that the first core member is removedfrom the lumen of the outer member without adversely affecting the outermember and the second core member.
 8. The method of claim 7, wherein thesecond core member comprises a radiopaque material.
 9. The method ofclaim 8, further comprising the step of filling the portion of the lumenof the outer member where the first core member was removed with abiologically or pharmacologically active substance.
 10. The method ofclaim 9, wherein the substance is selected from the group consisting ofantineoplastic, antimitotic, antiinflammatory, antiplatelet,anticoagulant, anti fibrin, antithrombin, antiproliferative, antibiotic,antioxidant, and antiallergic substances as well as combinationsthereof.
 11. The method of claim 7, further comprising the step ofproviding openings through the outer member to a portion of the lumen ofthe outer member wherein the first core member is disposed.
 12. Themethod of claim 11, wherein the step of providing openings through theouter member comprises laser drilling openings through the outer member.13. The method of claim 11, wherein the step of providing openingsthrough the outer member occurs before the step of processing thecomposite wire to remove the first core member.
 14. The method of claim7, wherein the outer member comprises a material selected from the groupconsisting of stainless steel, nickel-titanium alloys, andcobalt-nickel-chromium-molybdenum alloys.
 15. The method of claim 14,wherein the first core member comprises a material selected from thegroup consisting of tantalum, tungsten, molybdenum, niobium, rhenium,carbon, germanium, and silicon.
 16. The method of claim 15, wherein thesecond core member is formed from platinum or a platinum-iridium alloy.17. The method of claim 16, wherein the step of processing the compositewire comprises exposing the composite wire to xenon difluoride gas. 18.The method of claim 7, wherein the outer member is formed from MP35N,the first core member is formed from tantalum, and the second coremember is formed from a platinum iridium alloy, wherein the step ofprocessing the composite wire to remove the first core member comprisesexposing the composite wire to a xenon difluoride gas.
 19. The method ofclaim 7, wherein the outer member is formed from a material selectedfrom the group consisting of MP35N, L605, 316L stainless steel, thefirst core member is formed from a material selected from the groupconsisting of silver, copper, and aluminum, the second core member isformed from a material selected from the group consisting of tantalum,tungsten, platinum, and platinum-iridium alloys, and the step ofprocessing the composite wire comprises heating the composite wire to atemperature exceeding a melt temperature of the material of the firstcore member, but not exceeding a melt temperature of the outer member ora melt temperature of the second core member.
 20. The method of claim 7,wherein the outer member is formed from stainless steel, the first coremember is formed from copper, the second core member is formed fromplatinum or a platinum-iridium alloy, and the step of processing thecomposite wire comprises exposing the composite wire to nitric acid.